The percentage of an oral dose of mannitol, 3-O-methyl glucose, and lactulose excreted in urine is used in noninvasive investigation of active and passive intestinal mucosal transport. We developed a high-pressure liquid-chromatographic method involving anion exchange and pulsed electrochemical detection that allows the simultaneous determination of all three sugar probes in urine. Sample preparation is simple: diluting, mixing with internal standard (melibiose), and desalting. With use of a Dionex 250 x 40 mm Carbopac PA-1 column and elution with an isocratic mixture of 120 mmol/L NaOH and 0.5 mmol/L zinc acetate, all sugars were resolved within 10 min. The standard curve of the method is linear to the following concentrations: mannitol 125 mg/L, 3-O-methyl glucose 300 mg/L, and lactulose 40 mg/L. The minimal detectable concentration of lactulose is 0.4 mg/L. Analytical recovery of the sugars is between 89.0% and 99.5%. The precision of estimation (CV) ranges from 1.76% to 5.6% overall. Reference intervals were established from results for 28 healthy children. The method is adaptable for the study of carbohydrates at low concentrations in other biological fluids.